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Chemical Geology 312-313 (2012) 47–57
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Chemical Geology
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Research paper
Geology, age and field relations of Hadean zircon-bearing supracrustal rocks from
Quad Creek, eastern Beartooth Mountains (Montana and Wyoming, USA)
Analisa C. Maier a, Nicole L. Cates a, Dustin Trail a, b, Stephen J. Mojzsis a, c,⁎
a
Department of Geological Sciences, University of Colorado, 2200 Colorado Avenue, UCB 399, Boulder, CO 80309-0399, USA
Department of Earth & Environmental Sciences and New York Center for Astrobiology, Rensselaer Polytechnic Institute, Troy, NY 12180, USA
Laboratoire de Géologie de Lyon, Université Claude Bernard Lyon 1 and Ecole Normale Supérieure de Lyon, CNRS UMR 5276, 2 rue Raphaël DuBois, Bâtiment Geode 307,
69622 Villeurbanne Cedex, France
b
c
a r t i c l e
i n f o
Article history:
Received 23 September 2011
Received in revised form 4 April 2012
Accepted 9 April 2012
Available online 20 April 2012
Editor: L. Reisberg
Keywords:
Zircon
Hadean
Geochronology
Beartooth Mountains
Slave craton
Detrital
a b s t r a c t
Quad Creek Paleoarchean (≤3250 Ma) quartzites in southern Montana host Hadean (pre-3850 Ma) detrital zircons. Although an accessible resource for investigating early Earth processes distinct from other better known
ancient zircon localities, the outcrop-scale geological and geochemical context of these rocks has not previously
been well documented. New (1:250) mapping reveals a varied suite of isoclinally folded, sheared and variably
deformed chromite-bearing banded and massive quartzites, garnetiferous siliceous (migmatitic) paragneisses,
amphibolite, quartz–biotite schists and quartz+ magnetite rocks (banded iron-formation; BIF). Conventional
ion microprobe U–Pb zircon ages of populations from different quartzites and a paragneiss show outgrowth
rim ages on older inherited detrital igneous zircon cores that match documented regional metamorphic events
evidenced elsewhere in the Wyoming Craton. Weighted mean 207Pb/206Pb ages for the youngest concordant zircon cores of igneous derivation indicate the Quad Creek sediments were deposited by about 3250 Ma. Coupled
with a large zircon 207Pb/206Pb age survey (n= 1274), and an extended U–Th–Pb depth-profile of the oldest
grain in our sample set, these data support the notion that the oldest crust tapped by these sediments was comparable in age to the ca. 4000 Ma Acasta Gneiss Complex. This similarity is suggestive of both of a linkage between the Wyoming Craton and the Western Slave Province, and the lingering influence of Hadean crust well
into the Archean.
© 2012 Elsevier B.V. All rights reserved.
1. Introduction
The presence of significant granitic crust in the Hadean eon
(≥3850 Ma; definition of Bleeker, 2004) has been directly demonstrated through the discovery and characterization of hundreds of
thousands of zircons (Holden et al., 2009) – including an ancient population as old as 4370 Ma – found in quartzites within the Narryer
Gneiss Complex (NGC) at the Mt. Narryer (Froude et al., 1983) and
Jack Hills localities on the margins of the Yilgarn craton in Western
Australia (Compston and Pidgeon, 1986). Although alternative hypotheses have been offered for the genesis of these oldest zircons, including derivation from a mafic/gabbroic precursor (e.g. Galer and
Goldstein, 1991; Kemp et al., 2010), mineral chemistry arguments
most consistently favor granite–granitoid melt compositions (e.g.
Maas and McCulloch, 1991; Mojzsis et al., 2001; Trail et al., 2007;
Blichert-Toft and Albarède, 2008; Hopkins et al., 2008; Harrison,
2009; Hopkins et al., 2010; Trail et al., 2011).
⁎ Corresponding author at: Department of Geological Sciences, University of Colorado,
2200 Colorado Avenue, UCB 399, Boulder, CO 80309-0399, USA. Tel.: +33 4 72 44 58 07.
E-mail address: [email protected] (S.J. Mojzsis).
0009-2541/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.chemgeo.2012.04.005
It is worth mentioning that zircons this old are not exclusive to the
NGC. Elsewhere in Western Australia, Wyche et al. (2004) identified
detrital zircons from the Southern Cross Granite–Greenstone terrane
as old as 4350 Ma. However, the geographic proximity of the Southern
Cross terrane with the Narryer Gneisses could mean that they shared
the same crustal source of very old zircons. By and large, because
those studies are exclusively of detrital zircon grains orphaned from
their parent rocks, only broad inferences can be made about probable
source melt compositions that gave rise to them. Thus, ongoing debate
revolves around the precise nature of Hadean rock types that could
have given rise to the Hadean zircons (e.g. Valley et al., 2005; Kamber,
2007; Shirey et al., 2008; Kemp et al., 2010). No crustal remnants of
such great antiquity have so far been identified on Earth; they may be
buried, or they were destroyed long ago by, for example, the postulated
Late Heavy Bombardment of the inner solar system (e.g. Abramov and
Mojzsis, 2009).
As opposed to detrital zircon studies, direct analyses of Hadean
rocks are limited to the few localities where actual 4 billion-yearold crust is documented with certainty. These are the Acasta Gneiss
Complex (AGC) in the Northwest Territories of Canada (King, 1985;
Bowring et al., 1989; Stern and Bleeker, 1998; Bowring and
Williams, 1999), and certain components of the Mt. Sones gneisses
48
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
within the Napier Complex of Antarctica (Harley and Black, 1997 and
references therein). Although both the Acasta and Napier rocks are
evidently older than ca. 3900 Ma (cf. Moorbath, 2005), the geology
of their respective outcrops is as yet known only in broad terms,
and further complicated by protracted histories of high grade polymetamorphism and multiple episodes of intense deformation.
In addition, rare Hadean xenocrystic zircons have been found occluded in younger Eoarchean granitoid gneisses. One such 4183 Ma
grain was recovered in a drill core near Mt. Narryer (at the Jailor
Well) in Western Australia (Nelson et al., 2000). A concordant ca.
4200 Ma xenocrystic zircon was discovered by Iizuka et al. (2006,
2007) in tonalitic gneiss from the Acasta area, but the field context
of this sample is uncertain. A 3830–3850 Ma tonalitic orthogneiss
from Akilia (Nutman et al., 1997; Amelin et al., 2011) within the
southern Færinghavn terrane of the Itsaq Gneiss Complex (IGC) in
West Greenland, yielded a concordant 4100 Ma zircon encased in biotite (Mojzsis and Harrison, 2002). In spite of this isolated report, and
even though the IGC is regarded as the largest (>3000 km 2) and most
comprehensively studied Eoarchean–Paleoarchean terrane on Earth
(e.g. Nutman et al., 1996), no detrital zircons older than about
3890 Ma have been found there so far (Nutman et al., 2004).
Any new source of information on the Hadean Earth holds the potential to greatly enhance our understanding of the physical, chemical
and possibly biological mechanisms that shaped the young planet.
These would include: (i) the role of catastrophic impacts in the destruction of primordial crust; (ii) the plausibility of a nascent biosphere at that time; (iii) extent of continental-type crust; and (iv)
what geophysical events could have led to the initiation of plate tectonics. In order to advance what we know of the geology of those
places already identified to contain Hadean detritus, fine-scale mapping used to direct sample collection for geochronology and geochemistry of specific outcrops is warranted. With such knowledge,
we can begin to build hypothesis tests for the origin of the oldest detrital rocks and minerals as well as to expand our inventory of Hadean
crustal materials open for study.
One such example is from a fuchsite- (Cr-muscovite) bearing
quartzite which hosts rare (~ 2% yield) pre-3900 Ma detrital zircons
identified from samples in the northwestern part of the Wyoming
Craton at the Quad Creek locality in southern Montana (Mueller et
al., 1992, 1998; Fig. 1). The Quad Creek metasedimentary enclaves
are highly accessible at numerous road-cuts within granitoid gneisses
and migmatites along Montana Rte. 212 south of Red Lodge (town),
but remarkably little is known about their specific field relations.
Some sketch maps of the area were published previously (Mogk and
Henry, 1988), including a 1:600 scale map produced in the 1950s
(Eckelmann and Poldervaart, 1957). Yet, the actual association of ancient zircon-bearing quartzites with other lithotypes, what those lithologies are, as well as the various modes of zircon occurrence,
range of ages and compositions tied to specific lithologies, needs better definition. To this end, we performed 1:250 scale mapping to
guide sampling for geochronology and geochemistry of the associated
supracrustal rocks in the vicinity of the ancient zircon discovery site
(Mueller et al., 1992, 1996). We use the output of these studies to
propose a model for the origin of the various zircon populations.
2. Geologic background
The Beartooth Mountains form a 100 km long by 50 km wide
northwest-trending core of granite–granitoid gneisses flanked by
migmatites and supracrustal enclaves, and cut by mafic dykes and
leucogranitoid sheets (Fig. 1c). It has long been known (Schafer,
1937) that occurrences of chromite-bearing quartzites (e.g. the
metamorphic equivalents of heavy mineral “placer deposits”) and
paragneisses in the Wyoming Craton are scattered throughout the
b
a
Mueller et al. locality
ALASKA
Acasta Gneiss
Nain
Complex
Thelon
Basin
CANADA
Assean Lake
0 km
c
1200 km
Beartooth
Mountains
USA
Granitoid
Granitic gneiss
Migmatite
Amphibolite
Quartzite
Metanorite
45o2’30”
Interpreted contact
Road (US 212)
MEXICO
N
Archean rocks
Proterozoic rocks
< Proterozic rocks
1 km
Montana
Wyoming
109o 25’
Fig. 1. a. Generalized sketch map of Archean and Proterozoic rocks of North America. b. Discovery sample site of Mueller et al. (1992; sample “HRQ”). FOV = 200 m. c. Location map
(1:600) of the Quad Creek site in the Hellroaring Plateau, southern Montana. Modified from Eckelmann and Poldervaart, 1957 and updated with new data.
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
Metasedimentary Province. However, what was the source terrane of
the most ancient zircons at Quad Creek and surrounding supracrustal
enclaves? Something ancient was nearby because both Sm–Nd model
ages and whole-rock and mineral (feldspar) Pb isotope models show
that ca. 3900 Ma crust was present in the northern Wyoming province
when the Beartooth quartzites (and probably the whole of the MMP)
were deposited (Chamberlain and Mueller, 2007); whole-rock Hafnium
model ages of ca. 3850 Ma (Stevenson and Patchett, 1990) and zircon
Lu/Hf and εHf data (Mueller and Wooden, 2012) also support this view.
3. Methods
This study reports in detail on a small (185 × 210 m) area of outcrop with good exposure (~50–75%) that includes the discovery location of Mueller et al. (1992). New conventional zircon U–Pb ion
microprobe ages (n = 118) were combined with a large scale survey
( 204Pb-corrected) of detrital zircon age determinations (n = 1156)
to compare to all existing datasets of these rocks (Fig. 2).
“Conventional” ion microprobe geochronology in this case refers
to the routine U–Th–Pb analyses of zircons performed in spot mode
with the results averaged through 10–15 cycles of the secondary
ions accelerated through a large radius sector magnet before focusing
into an electron multiplier; because the primary ion beam is defocused to a ~ 20 μm diameter spot on the sample, the 2-D spatial selectivity of the ion microprobe is limited by the diameter of the primary beam. A variation of this technique termed "depth profiling" is
to extend the analysis time (~150–200 cycles) so that the primary
ion beam continues to sputter into the sample while at the same
time collecting data that is transformed into a continuous age and
composition profile of several micrometers (Mojzsis and Harrison,
2002). Further details of a depth-profiled ca. 4000 Ma grain (Bear2_5-6) from the Quad Creek locality described in Trail (2006) and
Trail et al. (2007) are reported here. In “rapid survey mode”, the ion
microprobe collects only the 204Pb, 206Pb, 207Pb and 208Pb secondary
ion beams into a multi-collector system of electron multipliers at
high primary ion beam currents in the span of less than 10 s per analysis (Holden et al., 2009). In this manner, age estimates for thousands
of zircons can be quickly determined. Our purpose in using this technique here was to explore the frequency of zircons of specific ages in
these Paleoarchean sediments via the statistics of large numbers.
When available, we also compared measured [Th/U]zrc for individual
zircon analyses with age against expected values for crystals grown
in an igneous environment, and as a function of ( 207Pb/ 235U age vs.
207
Pb/ 206Pb age) concordance (see Cates and Mojzsis, 2009). We
used these data to assess the probability density of geochronological
data tied to a particular composition (e.g. [Th/U]zrc) and ascribe a
10 2
Cumulative Frequency
northern and eastern Beartooth Mountains of southern Montana and
northern Wyoming. Archean basement uplifted during the Cretaceous Laramide Orogeny and sculpted by glaciers in the Pleistocene
means that outcrop exposure is good. The reason the Quad Creek outcrops have been the subject of study for so many years is that there
are many quality road cuts astride the part of the Beartooth granite
gneisses which hosts abundant supracrustal enclaves. The ~1000 m
relief of the area has steep canyon walls that also yields outcrop visible
in three-dimensions. At Quad Creek proper, a diverse suite of tectonically interwoven lithologies comprises mafic gneisses, quartzites and other
paragneisses, iron-formations, amphibolites, and some small outcrops
of biotite schists of uncertain affinity (Poldervaart and Bentley, 1958).
This kind of supracrustal assemblage is a general feature, for example,
of the North Snowy block of the Montana Metasedimentary Province
(MMP; Mogk et al., 1988, 1992) some 75 km northwest of the Quad
Creek outcrops. A supracrustal sample from the Tobacco Root Mountains ~175 km northeast of Quad Creek yielded a discordant 3930 Ma
zircon (Mueller et al., 1998), which testifies to a small background of
Hadean detritus in the wider region that awaits further exploration.
With the exception of the rare Hadean zircon record documented for
various supracrustal enclaves in the Wyoming Craton, periods of
Eoarchean and Paleoarchean crustal growth are inferred based on the
compositions of gneisses with ca. 3900 Ma Sm/Nd model ages and highly radiogenic Pb isotopic compositions (Wooden and Mueller, 1988).
These include rocks of the Sacawee block and MMP (Grace et al.,
2006) as well as 3300–3700 Ma ages for the Granite Mountain region
of central Wyoming (Fisher and Stacey, 1986; Langstaff, 1995). Ancient
(ca. 4100 Ma) model ages have also been derived from interpretations
of trends in calculated initial εHf values for Quad Creek zircons
(Mueller and Wooden, 2012).
The Quad Creek rocks experienced magmatic injections probably
associated with the final assembly of the Wyoming Craton; magmatism occurred in three separate phases in the southern margin of
the terrane at 2710–2670, 2650–2620, and 2550–2500 Ma (Mueller
and Frost, 2006). Proterozoic extension at 2100–2000 Ma and
1500–1400 Ma is also recognized, which saw the emplacement of
mafic dike swarms associated with crustal thinning (Chamberlain et
al., 2003). The Beartooth rocks were brought to granulite facies metamorphic conditions (T = 750–800 °C, P = 5–6 kbar) sometime around
3250–3100 Ma (Henry et al., 1984) based mostly on Rb–Sr and Pb–Pb
systematics and other indicators (Wooden et al., 1988a,b; Mogk et al.,
1992). Granulite metamorphism was followed by retrograde amphibolite facies metamorphism and several later episodes of granitoid intrusions (Eckelmann and Poldervaart, 1957; Mogk and Henry, 1988).
Various results from ongoing geochronological work on detrital
and younger post-depositional (metamorphic) zircons from the
northern part of the Wyoming Province were used to constrain a
broader age range of 2700–3300 Ma for the quartzites (Mueller et
al., 1988; Mueller and Wooden, 2012). The overall dominance of ca.
3300 Ma ages in all zircon U–Pb datasets thus far published could
also be interpreted as representative of the maximum age of deposition of these supracrustals, if it can be shown that the youngest
most concordant zircons in this age grouping have Th/U compositions
consonant with equilibrium exchange of Th and U with magma (see
below). In a study of 355 detrital zircons from the original Quad
Creek sampling locality by Mueller et al. (1992, 1998), about 20% of
the grains were found to be between 3400 and 4000 Ma and many
of those were within 10% of concordia. More recently, Mueller and
Wooden (2012) reported ages and Hf isotope compositions for 75
more zircons from Quad Creek (Fig. 2). Datasets from the neighboring
Ruby and Tobacco Root uplifts show that they too are no younger
than about 3250 Ma (Mueller and Frost, 2006).
Overall, there is general agreement that the Paleoarchean igneous
(as opposed to younger neoform metamorphic) zircon ages reflect the
dominant influence to these sediments from crust of that age shed
into the catchments (basins) that ultimately formed the Montana
49
This work
Mueller & Wooden (2012)
Trail (2006)
Mueller et al. (1992)
10 1
10 0
2000
2250
2500
2750
3000
3250
3500
3750
4000
Age (Ma)
Fig. 2. Comparative cumulative frequency plots of Beartooth Mountain zircon 207Pb/206Pb
ages from this study (dark gray), Mueller et al. (1992; hashed lines), Mueller and Wooden
(2012; light gray), and Trail (2006; black line, white fill).
50
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
maximum age for deposition of the Quad Creek sediments from the
ages of the youngest detrital zircon of igneous heritage. Acquisition
of whole-rock major-, minor- and trace element geochemistry is
also described below. Collectively we used these data to assign protolith(s) based on mineralogy and composition, and maximum ages of
deposition of igneous zircons to suggest geochemical links with
other ancient rock localities mentioned above.
3.1. Field mapping
The Quad Creek exposure was mapped with a 25 × 25 m E–W oriented grid (Fig. 3) annotated to show sample locations with photodocumentation of specific outcrops discussed in the text. The focus
of the work was on quartzites which could contain detrital zircons.
Overall, the exposure is dominated by strongly deformed isoclinally
folded supracrustal rocks comprising abundant massive quartzites
(Aqm) and banded paragneisses (Aqb) with locally highly-variable
fuchsite contents (labeled f on the map where locally enriched in
Cr-mica). Paragneisses range from massive to banded and patchily
garnetiferous (gt); these are cut by at least one generation of mafic
dikes (Md). Subordinate units include a finely banded but strongly
deformed and sheared quartz magnetite rock (BIF s.l.) restricted to
the easternmost mapped area and bordered by garnet-bearing amphibolite (Amg). No carbonates were noted here (cf. Mogk et al.,
1992). The sheared east–west trending isoclinal folding within the
supracrustal sequence is not a structure shared by the underlying
massive intrusive granitoid (trondhjemitic) gneisses (Gb). To the
best of our knowledge, the original sampling locality of old detrital
zircons reported by Mueller et al. (1992) is within gray-green quartzites directly at a road cut of Montana Rte. 212 at the western boundary of the mapped area as indicated in Fig. 1b.
3.2. Ion microprobe U–Pb zircon geochronology
Ion microprobe U–Pb zircon geochronological analyses of zircons
from two supracrustal lithologies (three quartzite samples Aqm, and
three paragneiss samples Agb) are reported in the Supplementary
data accompanying this paper (Table S.1). Rock samples were prepared for geochemistry and zircon separations using standard techniques (e.g. Cates and Mojzsis, 2006, 2007) and a brief summary is
provided here: approximately 5 kg of Aqm samples BT0606, -08 and
‐11 and Agb samples BT0603, -04 and ‐10 from the mapped area,
and 10 kg of sample BT1 – previously collected from the “HRQ”
location noted in Mueller et al. (1998) – were chosen for zircon extractions. These large samples were reduced by crushing and sieving
to b350 μm. Geochemistry for sample BT1 is not reported here but mineralogically it is identical to Aqm sample BT0606 and mapping shows
they are part of the same unit. Powders for zircon extractions went
through two stages of clean heavy liquid separations, rinsing in
reagent-grade acetone and ultrapure water, followed by hand-magnet
and then two stages of Frantz magnetic separations to screen out minerals of different magnetic susceptibilities from the densest residues. Individual zircons were handpicked from the least magnetic grain
fractions under a binocular microscope and a wide spectrum of morphologies and aspect ratios were chosen to diminish sampling bias.
These were placed on double-sided adhesive tape and cast in 2.52 cm
diameter molds with Buehler© epoxide resin alongside grains of standard zircon AS3 (Paces and Miller, 1993; Black et al., 2003). The sample
disks were then beveled and polished in stages to 0.25 μm alumina until
grain centers were exposed. Transmitted and reflected optical micrograph mount maps were created, followed by imaging with backscattered electrons of polished centers on a JEOL JXA-8600 electron
microprobe at the University of Colorado under standard operating
conditions. To reduce common Pb contamination prior to ion microprobe analysis, all grain mounts were pre-cleaned in 1 N HCL solution
at room temperature, washed in ultrapure water, air dried in a 50 °C
oven, and sputter coated with ~100 Å of Au to facilitate conductivity.
All conventional zircon U–Pb ion microprobe geochronology on our
sample zircons was performed using the UCLA Cameca ims1270 highresolution SIMS under standard operating conditions (e.g. Cates and
Mojzsis, 2006), a brief synopsis is provided here: a ~6-nA O2− primary
beam was focused to a 25‐μm spot and operated at a mass resolving
power of ΔM ~6000 to exclude molecular interferences. To increase the
Pb+ ion yields, oxygen flooding to a pressure of 2.7×10− 5 Torr was
used (Schuhmacher et al., 1994). Ages for unknown zircons were determined by comparison with a working curve defined by multiple measurements of standard AS3 that yields concordant 206Pb/238U and 207Pb/235U
ages of 1099.1±0.5 Ma. Data were reduced and the output used to construct Tera-Wasserburg diagrams (207Pb/206Pb vs. 238U/206Pb) with the
Isoplot software package (Ludwig, 2003). All individual conventional
ion microprobe zircon ages are reported at the 1σ level based on asymmetric weighted regressions except when noted. For our large-scale
204
Pb-corrected age survey (sample BT-1) we used the Australian National University SHRIMP-II in automated mode on two separate zircon
mounts; analytical conditions as well as relative accuracies for individual
age estimates are described in Holden et al. (2009) and data are reported
in Table S.2.
N 45° 01.899
BT0606
Aq
f
BT0607
BT0602
Agb
Md
BT0608
76
S80W
f
f
38
Gb
f
f
212
gt
cliff 38
Agb
38
BT06010
BT0603
Agb
gt
BT1001
Aq
f
gt
BT0609
f
Am
Aq
Agb
Am
BT0605 f
64
cliff
58
f
58
58
BT0604
Aq
212
Agb
Gb
N
BT1004
W 109° 25.456
Agb
3.3. Whole-rock geochemistry
Duplicate whole-rock sample splits were prepared by subdividing
~2 kg unweathered rock pieces and powdering in pre-cleaned ceramic
mills. Analysis of major-, minor- and trace elements (Table 1) was undertaken by XRF and ICP-MS at Activation Laboratories (ACTLABS; Ontario, Canada). Comparison of recommended and analyzed standards
from ACTLABS show small deviations (b1.5%) for oxides, except MnO
(6.3%), Na2O (6.5%) and P2O5 (23.1%) and for trace elements b20% relative, except Ni (21.4%), Pr had a 47.6% relative error. Granitoid rock assignments are from Barker (1979) based on normative modes of albite
(Ab), orthoclase (Or) and anorthite (An); (trond= trondhjemite).
4. Geochemical results and sample descriptions
BT0611
BT1006
Am
Aq
Quartzite
Agb Paragneiss (banded)
20 m
Gb
Md
Am Amphibolite
Banded Iron Formation
Trondhjemite
58
Sample location
f Fuchsite-rich
gt Garnet-bearing
Fold Hinge
Strike/Dip
Fig. 3. Geologic map (1:250) of the Quad Creek study area.
4.1. Quartzites (Aqm) BT0606 (45°01.890′ N, 109°24.560′ W), BT0608
(45°01.881′ N, 109°24.550′ W), BT0611 (45°01.839′ N, 109°24.631′ W)
The dominant rock type exposed in the mapped area is a quartzite
with local dark green micaceous banding. Most are massive, gray to
greenish in color. However certain sections locally preserve distinctive
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
51
Table 1
Representative bulk-rock compositions from Quad Creek, southern Montana.
Lithotype
Md
Aqm
Aqm
Agb
Aqm
Aqbc
Gb
BIF
Sample #
BT0602
BT0606
BT0608
BT0610
BT0611
BT1002
BT1004
BT1006
SiO2
Al2O3
Fe2O3(T)
MnO
MgO
CaO
Na2O
K2O
TiO2
P2O5
LOI
Total
Sc
Be
V
Cr
Co
Ni
Cu
Zn
Ga
Ge
As
Rb
Sr
Y
Zr
Nb
Mo
Ag
In
Sn
Sb
Cs
Ba
La
Ce
Pr
Nd
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
Hf
Ta
W
Tl
Pb
Bi
Th
U
Y/Ho
47.58
14.46
12.54
0.204
9.54
10.93
2.29
0.55
0.823
0.06
1.66
100.6
46
b1
319
310
54
140
20
100
16
1.7
b5
15
113
18.4
45
1.5
b2
b0.5
b0.1
b1
0.3
b0.1
46
2.74
7.04
0.9
4.78
1.82
0.603
2.43
0.47
3.09
0.65
1.95
0.304
2.1
0.353
1.2
0.14
0.7
0.06
b5
b0.1
0.76
0.42
28.30769
93.46
4.57
0.22
0.004
0.1
0.04
0.65
0.88
0.023
0.03
0.77
100.7
b1
b1
6
40
1
b 20
b 10
b 30
5
0.6
b5
30
25
1.5
65
0.5
b2
b0.5
b0.1
b1
0.4
0.2
183
21.8
38
3.16
10.3
1.42
0.345
0.89
0.09
0.39
0.06
0.14
0.019
0.12
0.018
93.18
4
0.81
0.011
0.41
0.32
0.53
0.54
0.144
b 0.01
0.84
100.8
4
b1
16
90
4
b20
b10
b30
6
0.8
b5
23
22
3.6
81
1.6
b2
b 0.5
b 0.1
b1
b 0.2
0.6
200
15.7
30.5
2.74
9.72
1.51
0.18
1.05
0.13
0.67
0.12
0.31
0.047
0.34
0.062
1.9
0.21
b 0.5
0.1
b5
b 0.1
8.31
0.81
30
75.09
13.66
1.41
0.009
0.25
0.35
1.37
6.23
0.203
0.03
0.73
99.34
3
b1
52
230
12
30
40
b 30
19
b0.5
b5
126
169
2.1
348
1.2
b2
0.8
b0.1
b1
0.3
0.7
1173
41.6
73.1
6.08
20.4
2.42
1.02
1.04
0.09
0.42
0.08
0.24
0.042
0.35
0.086
8.3
0.07
b0.5
0.55
15
b0.1
18
1.44
26.25
94.96
2.86
0.69
0.004
0.17
0.03
0.14
0.65
0.078
b0.01
0.63
100.2
2
b1
13
360
8
b 20
40
b 30
6
0.9
b5
12
14
1.3
37
0.5
b2
b0.5
b0.1
b1
b0.2
0.2
195
6.07
10.7
1.09
3.58
0.58
0.173
0.42
0.05
0.29
0.05
0.15
0.023
0.16
0.027
0.8
0.07
b0.5
0.06
b5
b0.1
3.14
0.63
26
77.26
14.34
0.76
0.028
0.52
3.13
2.59
0.88
0.165
0.03
1.2
100.9
3
b1
27
70
10
40
b 10
b 30
15
1.2
b5
21
121
5.5
49
1.7
b2
b0.5
b0.1
b1
b0.2
0.5
429
24.1
40.8
4.18
14
2.34
1.47
1.78
0.23
1.17
0.19
0.49
0.062
0.34
0.046
1.2
0.14
b0.5
0.1
8
b0.1
5.85
0.6
28.947368
72.58
15.35
1.37
0.016
0.36
2.08
4.98
2.09
0.166
0.05
0.72
99.77
2
b1
13
b20
2
b20
b10
290
20
0.8
b5
48
256
5.9
167
2.6
b2
b 0.5
b 0.1
b1
b 0.2
1.1
584
40.6
71.8
5.95
19.6
3.2
0.567
2.14
0.27
1.31
0.2
0.47
0.057
0.32
0.042
3.7
0.24
b 0.5
0.23
27
b 0.1
25
1.46
29.5
43.84
2.9
50.84
0.376
2.22
1.82
0.04
0.04
0.104
0.16
− 1.45
100.9
3
b1
34
50
6
b 20
20
80
5
6.5
b5
1
8
8.6
26
8.1
b2
b 0.5
b 0.1
1
1.4
b 0.1
33
2.41
5.68
0.77
3.34
0.92
0.256
1.08
0.21
1.4
0.3
0.93
0.146
1.04
0.175
0.7
0.07
b 0.5
b 0.05
b5
b 0.1
2.44
0.78
28.666667
0.06
b0.5
0.1
10
b0.1
6.89
0.44
25
Notes: Major elements reported as wt.% oxides; all others in ppm.
“sedimentary” bands rich in chromite, sulfide, Cr-mica, zircon and other
minerals; some of these appear to show cross-bedding. Bulk compositions of the Aqm rocks are strongly enriched in SiO2 (93.2–95 wt.%) befitting their protolith as typical Archean “super-mature” quartz sands
with a heavy mineral suite dominated by zircon, chromite and rutile
and the narrow variability in SiO2 content is accompanied by different
relative abundances of heavy minerals. The quartzites have Al2O3 contents that vary by a factor of ~2 (2.86–4.57 wt.%). Different quartzite
samples show an order-of-magnitude range of Cr abundances
(40–360 ppm) but generally lower Zr concentrations (37–81 ppm) compared to granitoids. Primitive mantle normalized multi-element plots
(Fig. 4) show negative Nb, Sr, and Ti anomalies consistent with weathering and transport from prevailing felsic sources to the sediment with a
small mixture of mafic component. Chondrite normalized REE patterns
also display enriched LREE and depleted HREE, with a negative Eu anomaly observed only in sample BT0608.
4.2. Paragneiss (Agb) BT0610 (45°01.866′ N, 109°24.632′ W)
A suite of banded quartz ± garnet paragneisses appear in the field
as white to gray rocks with bands of darker more mafic minerals rich
in garnet. In outcrop, they tend to weather to a beige-orange color.
52
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
b
1000
100
10
1
0.1
Sedimentary Protoliths
BT0606 (Aqm)
BT0608 (Aqm)
BT0611 (Aqm)
BT0610 (Agb)
BT1006 (BIF)
Primiative Mantle (PM) normalized
Chondrite normalized
a
d
10
1
Igneous Protoliths
BT1002 (Aqbc)
BT1004 (Gb)
BT0602 (Md)
0.1
La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
Primiative Mantle (PM) normalized
Chondrite normalized
1000
100
100
10
1
Sedimentary Protoliths
0.1
BT0606 (Aqm)
BT0608 (Aqm)
BT0611 (Aqm)
BT0610 (Agb)
BT1006 (BIF)
0.01
Rb Ba K Th Nb La Ce Sr Nd Zr Eu Ti Dy Y Er Yb
La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
c
1000
1000
100
10
1
0.1
Igneous Protoliths
BT1002 (Aqbc)
BT1004 (Gb)
BT0602 (Md)
0.01
Rb Ba K Th Nb La Ce Sr Nd Zr Eu Ti Dy Y Er Yb
Fig. 4. (a, c) Chondrite-normalized REE plots, and (b, d) primitive mantle-normalized multi-element plots of the different lithologies in the Quad Creek study area.
Sample BT0610 has a similar Cr-enrichment (230) ppm to some
quartzites, but has lower SiO2 contents (75.09%) and is relatively
enriched in alumina (13.66%). Zirconium content is greatly elevated in
the paragneiss with respect to the typical Aqm lithologies (348 ppm)
which may denote its origin as less mature quartz-rich to pelitic sediments. In a multi-element plot, the Agb rocks show negative Sr and Ti
anomalies along with a concave-upward trend from Dy to Yb. Overall
REE contents show enriched LREE compared to HREE with a positive Eu
anomaly.
4.3. Quartz-magnetite rock (BIF) BT1006 (45°01.829′ N, 109°24.572′ W)
A small and narrow outcrop of silicate-facies BIF is sandwiched between sections of an amphibolite which defines a tight fold axis that
plunges eastwards. On the map, the amphibolite limbs are bounded
by quartzites on one side and trondhjemite on the other (Fig. 3).
The amphibolite was not sampled for geochemistry. The BIF unit is
iron rich (51 wt.% Fe2O3) with 44% SiO2 and minor Al2O3 (~3%). It
also contains 50 ppm Cr and 26 ppm Zr consistent with a small detrital component. Trends in primitive mantle-normalized multi-element
REE plots reflect this in negative Sr and Ti anomalies and show that
the BIF has some similarities to the quartzites and paragneiss with
which it is (presumably) co-genetic in the supracrustal sequence. In
a chondrite normalized REE plot, LREE are enriched over HREE and
show a small negative Eu anomaly. With respect to the Y/Ho ratio,
the Quad Creek quartz–magnetite rock is low (28.7) in comparison
to most Archean BIFs (Bolhar et al., 2004), as well as relatively low
in molar Ni/Fe (Konhauser et al., 2009) and Cr contents (Konhauser
et al., 2011) compared to averages for other BIFs of broadly similar
age (ca. 3300 Ma).
4.4. Trondhjemitic Granitoid Body (Gb) BT1004 (45°01.783′ N,
109°24.468′ W) and quartz–biotite schist (Aqbc) BT1002 (45°01.860′
N, 109°24.642′ W)
In several places within the supracrustal succession, pockets of a
granitoid penetrate through the outcrop, and the whole locality is underlain by a large body of trondhjemitic compositions (BT1004) as
defined by normative Ab–An–Or of Barker (1979) (Fig. S.1). We also
identified a quartz–biotite schist (conglomerate? BT1002) near the
base of the Rte. 212 road cut and slightly west of sample site HRQ
(Fig. S.2). As this rock was not found to crop out in the mapped area
it is not marked on the map but we interpret it to be part of the
same package of supracrustals near the “base” of the sequence. Both
the quartz–biotite schist and the trondhjemite show similar SiO2
and Al2O3 values to the paragneiss with 77.3% SiO2, and 14.3% Al2O3
for the conglomerate and 72.6% SiO2 and 15.4% Al2O3 for the trondhjemite, respectively. The quartz–biotite schist contains 70 ppm Cr and
49 ppm Zr, whereas the trondhjemite is Cr-poor (below detection
limit), and relatively low in Zr (167 ppm) compared to granites but
is entirely consistent with trondhjemite.
4.5. Mafic Dike (Md) BT0602 (45°01.879′ N, 109°24.671′ W)
Sample BT0602 is a black to dark gray unit bordered by paragneisses. It contains 47.58% SiO2, 14.46% Al2O3, 12.54% Fe2O3, and
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
10.93% CaO with 310 ppm Cr and 45 ppm Zr. To determine if the
mafic dike is part of the calc-alkaline or tholeiite series, we plotted
its composition on a AFM diagram but this was inconclusive as the result lies between the determining lines of Kuno (1968) and Irvine and
Baragar (1971) (Fig. S.3). However, on a K2O vs. silica diagram, using
the subdivisions of Rickwood (1989) the mafic dike appears more
akin to calc-alkaline magmas with medium to low K.
5. Geochronological results
5.1. U–Pb zircon ion microprobe geochronology with correlated [Th/U]zrc
During crystal growth in magmas, zircons partition trace elements
such as REEs, U and Th in predictable ways, and this incorporation can
be de-convolved to values reflective of crustal compositions. As outlined in Mojzsis and Harrison (2002), zircons grown from melts with
Th/U values typical of crust (~4; Taylor and Mclennan, 1985) are expected
zrc/melt
to have a [Th/U]zrc ~0.8±0.2 provided that DTh/U
=0.2±0.15 (e.g.
Mahood and Hildreth, 1983; Blundy and Wood, 2003). On the other
hand, zircons grown in aqueous metamorphic fluids, from solid-state recrystallization, or via hydrothermal growth, tend to deviate strongly in
[Th/U]zrc compared to the relatively narrow range ([Th/U]zrc ~0.4–0.8) of
ordinary igneous values. Many (but not all) metamorphic zircons preserve exceptionally low [Th/U]zrc values, frequently ~10− 1–10− 3 (e.g.
Rubatto, 2002). This [Th/U]zrc criterion has been used in conjunction
with other indicators such as Tixln temperatures and REE partitioning calculations (e.g. Trail et al., 2007; Cates and Mojzsis, 2009) to discriminate
zircon domains of igneous derivation from those wholly or in part of
non-igneous origin. We applied this test to investigate [Th/U]zrc vs.
207
Pb/206Pb ages for zircons reported here and in the literature.
Zircons were extracted from three fuchsitic quartzites (BT0606,
-08 and ‐11) and three (banded) paragneisses (BT0603, BT0604,
and BT0610) from the mapped area shown in Fig. 3. Values of
[Th/U]zrc vs. age (Fig. S.4) for data ≤ 30% discordant appear similarly scattered for different age bins and vary by several orders of magnitude in [Th/U]zrc. Filtering data to the least disturbed ages (b5%
discordant; Fig. 5) yields distinct age groupings at (i) 2800 Ma with a
[Th/U]zrc ~ 1.1 × 10 − 2 (ii) 3300–3100 Ma ([Th/U]zrc = 0.14–1.5);
(iii) 3400–3500 Ma ([Th/U]zrc = 0.32–.57); and (iv) ≥ 3700 Ma with
[Th/U]zrc of 0.35–0.45. Eoarchean to Hadean (3650–3902 Ma) zircons were found in several of the banded paragneiss samples in our
53
mapped area, but the majority of ages reside in the ca. 3300 Ma population. As expected, younger (metamorphic) zircons show a large
scatter in [Th/U]zrc with ratios mostly well below that expected for
igneous compositions. Fig. 6 shows that there is a pronounced age
grouping at ca. 3250 Ma and ca. 3450 Ma with [Th/U]zrc consonant
with igneous derivation (0.4–0.5) for the peak around 3450 Ma,
and more variable ratios for younger zircons at about 3250 Ma
(range of [Th/U]zrc = 0.4 to 1.2). A subset of 3200 Ma and younger zircons is also evident with variable (but low) [Th/U]zrc as well as internal
textures (Fig. S.5) visible in electron microscopy (spongy appearance,
abundant inclusions, mundane/faint/sector zoning, absence of zoning)
that are attributable to in situ metamorphic growth (Corfu et al., 2003;
Hoskin and Schaltegger, 2003) likely during one of several of the metamorphic episodes described above.
The 3250 Ma zircons are of igneous origin, as shown by their
[Th/U]zrc values. Thus 3250 Ma represents a putative maximum
age for the quartzites and paragneisses, in general agreement
with previous work (Chamberlain and Mueller, 2007; Mueller and
Wooden, 2012). Of the 118 zircons analyzed in this study by conventional U–Pb zircon geochronology, 70 were less than 30% discordant.
One of the four oldest zircons in our analysis pool (3866 Ma) is from
the paragneiss (Agb sample BT0610), and the three others (3902,
3756, and 3690 Ma) are from two fuchsitic quartzites (Aqm sample,
BT0608 and BT0611). Altogether, we find that our age populations
from both conventional and survey-mode ion microprobe zircon geochronology tend to be somewhat younger than the oldest ages in the
data tables published in Mueller et al. (1992) and Mueller and
Wooden (2012) (Fig. 2).
5.2. U–Th–Pb depth profile of the oldest zircon at Quad Creek
Approximately 10 kg of sample BT-1 (HRQ of Mueller et al., 1992)
yielded thousands of zircon grains of diverse morphologies (Trail,
2006). From this sample pool we prepared two polished zircon
grain mounts for large scale geochronological surveys; this work
this work
Mueller (1992, 2012)
Bear-2_5-6
Sircombe et al. (2001)
Bohm et al. (2003)
<5% discordant
[Th/U]zrc
100
[Th/U]zircon
10-1
2275 2450 2625 2800 2975 3150 3325 3500 3675 3850 4025
207Pb
207
Pb/
206
Pb
Fig. 5. Plot of relative probability and [Th/U]zircon vs. 207Pb/206Pb zircon age filtered for
analyses that are b 5% discordant reported in Table S1.
/ 206Pb age (Ma)
Fig. 6. Probability density plot of [Th/U]zrc vs. 207Pb/206Pb age based on data reported
here (see legend), Trail et al. (2007), Mueller et al. (1992), the average oldest, most
concordant zircon from the Assean Lake Complex (Böhm et al., 2003), and the oldest
most concordant zircon from the Central Slave Cover Group (Sircombe et al., 2001).
The different colors are of increasing probability density; blue is least dense and red
is most dense. There is one broadly distinctive age vs. [Th/U]zrc cluster with a calculated
age of 3250 Ma and igneous [Th/U]zrc values. Similar ages and Th/U ratios are evident
for the oldest Quad Creek zircons in this study to those reported from other ancient detrital zircon localities in North America.
54
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
yielded two zircons with ages ≥3960 Ma, later verified by depth profile analysis on one grain (Bear-2_5-6) to have a weighted mean age
of 3997 ± 5 Ma (2σ; mswd = 1.9) and [Th/U]zrc = 0.503 ± 0.002
(Table S.3). Zircon sample BEAR-2_5-6 is thus far the oldest zircon
documented from the Quad Creek locality and it is of unambiguous
igneous origin.
In the tabulated data points provided by Mueller et al. (1992), two
pre-3900 Ma HRQ zircons were within 1% of concordia: their “grain 6”
was 3964 Ma [Th/U]zrc = 0.403 and “grain 45” had an average age of
3936 Ma and [Th/U]zrc = 0.513, that was nearly identical to our zircon
sample Bear-2_5-6. That these oldest grains are large (~ 120–160 μm),
concordant zircons with a limited range of igneous [Th/U]zrc values
can in principle provide clues as to their source rocks. New data
reported in Mueller and Wooden (2012) extend this theme further
with 75 documented data points; the five oldest zircons reported
therein are within 3% of concordia and range in age from 3910 Ma
([Th/U]zrc = 0.34) to 3981 Ma ([Th/U]zrc = 1.05).
6. Discussion
Zircon geochronology for the Quad Creek rocks shows evidence of
three different events, the precise geological order and context of
which are uncertain due to the deformational overprint and the limited information from beyond the mapped area.
6.1. Geochronological relations at Quad Creek
Based on what is known so far, the first event in its history was the
establishment in the Paleoarchean of a sedimentary depo-center typified by psammitic quartzites rich in detrital placer minerals (chromite,
minor sulfides and zircon), emplacement of the protolith to the amphibolite (as extrusive basalt?) and deposition of the BIF around
3250 Ma. The stratigraphic context and order of these events is unclear.
This appears to have been followed by a period of deformation coinciding with metamorphism at the granulite facies beginning at ca.
3200 Ma. Afterwards, crustal thinning was accompanied by the intrusion of mafic dikes. Subsequently, an intrusive trondjhemite/granodiorite was responsible for local partial melting of the sediments. Finally,
a quartz and biotite leucogranitoid was emplaced in and around the
supracrustal rocks. Pervasive hydrothermal alteration affected much
of the area. Uplift was followed by denudation and erosion of younger
rocks to expose the oldest core of the Beartooth Mountains.
6.2. Zircon morphology
The uncertain distinction between zircons of (primary) igneous,
or (secondary) metamorphic and hydrothermal origin continues to
befuddle age analysis in ancient complexes. However, different petrogenetic origins of different zircon populations in the same rock can sometimes be reconciled on crystal chemical grounds (Th/U, REE partitioning,
Tixln; e.g. Cates and Mojzsis, 2009) coupled with morphological analysis
of grain habit and internal texture. Igneous zircons tend to have relatively
high aspect ratios and are euhedral due to their semi-continuous growth
in a magma chamber; detrital zircons of whatever petrogenetic origin
tend to be rounded because they get abraded during sedimentary transport. As outlined in Corfu et al. (2003) metamorphic zircons can have a
host of textures depending for the most part on host rock composition
and degree of metamorphism.
Zircons in this study – collected from sedimentary protoliths – tend
to have subhedral habit with variable aspect ratios; based on morphology correlated with composition it is certain that some grew in situ during metamorphism, others have overgrowths on rounded cores, and
still others show complex internal morphologies indicative of resorption/recrystallization (Fig. S.5). Back-scattered electron images of the
oldest and most concordant zircons in this study (>3.6 Ga) show that
they are subhedral and display clear overgrowths consistent with
neoform zircon growth, re-melting, resorption and/or recrystallization
(e.g. Hay et al., 2010). For example, sample grain #1 of BT0611 (sample
BT0611_1), as well as BT0608_6, and BT0610_5, are cracked with
rounded tips, while one of the oldest zircons in our sample suite:
BT0608_4 (3902 Ma) shows little to no fracturing with quite angular
(sub-rounded) tips. Twinning (BT0608_4) is also observed.
Gross morphological analysis in BSE and optical microscopy of
some of the youngest demonstrably igneous age populations (from
3400 to 3500 Ma) show that they are sub-rounded inclusion-rich
grains with obvious rim overgrowths; zircons of this age population
are generally within a few percent of concordia. The youngest igneous
zircons from within the ca. 3300 Ma population tend to be euhedral
with metamorphic rims, and are generally concordant. All zircons
equal to or younger than about 3200 Ma are stubby crystals with
some fracturing, and are rich in inclusions. A significant proportion
of grains from this grouping are >30% discordant and show evidence
for radiation damage in BSE images. The youngest metamorphic
populations (2700–2900 Ma) show a wide variety of habit from highly rounded to broken with fracturing and overgrowths with highly
variable concordance.
6.3. Zircon chemistry
The Th/U values of the zircons from the paragneiss and quartzites
are comparable (Fig. 6) and suggestive of the same sediment source.
Making sense of the overall highly variable ≤30% discordant zircons
with diverse [Th/U]zrc ratios (Fig. S.4) remains problematic unless
they are separated in terms of U–Pb age populations. We interpret
the large scatter in [Th/U]zrc for the 3200 Ma age grouping as representative of the first widespread metamorphic event that triggered
zircon growth in the granulite facies (Mueller et al., 1998). This is a
feature that has been widely documented for other ancient supracrustal rocks which have experienced ancient and protracted high
grade metamorphic histories (e.g. Manning et al., 2006).
6.4. Geochemistry and protolith assignment
Sample BT0608 was mapped as a paragneiss, however, the geochemistry shows its protolith is closer to quartzitic; it should be noted
then that the quarztite may extend down further in this location or
the paragneiss and quarztite are intermixed here. In a multi-element
diagram (Fig. 4), felsic lithologies (detrital and igneous) show enriched
large ion lithophile elements, and negative Nb anomalies with depletions in Sr and Ti for all lithologies except the mafic dike. This would
seem to indicate that both the quartzites and paragneiss had the same
source. Paragneisses and quartzites follow expected weathering trends
(Nesbitt and Young, 1989) for a mixed granitoid+ mafic source; higher
proportions of quartz led to the quartzites, with less mature sediments
represented by the paragneisses (Fig. 7).
6.5. Widespread detrital contamination from an ancient “Slave Continent”
in the Archean?
Soon after their discovery, it was realized that the oldest ages for the
Beartooth zircons were akin to those of the oldest tonalitic and granodioritic gneisses in the ca. 4000 Ma Acasta Gneiss Complex (AGC). The
AGC is about 2250 km to the north of Quad Creek at the westernmost
margin of the Slave craton, Northwest Territories, Canada (Bowring
and Williams, 1999). Its areal extent is at least 180 km2 (Iizuka et al.,
2007 and references therein); what exists now almost certainly represents the last vestige of a much larger block (Bleeker, 2003). Presently,
the main exposure of the AGC is dominated by layered mafic gneisses
and felsic gneisses with blocks of mafic–intermediate gneisses (Iizuka
et al., 2007). The oldest components of the AGC were emplaced in the
timeframe 4030–3940 Ma, but record evidence for possibly older
rocks from a 4200 Ma xenocrystic zircon (Iizuka et al., 2006). The initial
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
AGC magmatic emplacement was followed by two Eoarchean igneous
intrusions at 3740–3720 Ma and 3660–3590 Ma. The last of these was
accompanied by crustal anatexis and recrystallization of older units
(Bowring and Housh, 1995; Iizuka et al., 2007). Subsequent intrusions
and modifications of the AGC continued into the Proterozoic, culminating with regional metamorphism at 1900–1800 Ma related to the
Wopmay Orogen (King, 1985; Sano et al., 1999). Many of these pre3300 Ma AGC ages find complements in the zircon age spectra for
Quad Creek and we can begin to ask if there exists a wider context of
Hadean detritus in Archean metasediments of North America.
Approximately 1500 km to the northeast of the Beartooth Mountain
locality, ca. 3900 Ma ages for detrital zircons have been reported in the
Assean Lake Complex (ALC). The ALC is a ~120 km2 west–northwest
trending slice of largely Neo- to Mesoarchean rocks bounded to the
north by the Paleoproterozoic Trans-Hudson Orogen and the Neoarchean
Northwest Superior Province to the south (Böhm et al., 2000, 2003, 2007).
Within the ALC there are at least two ca. 3200–3250 Ma supracrustal
packages of quartz–biotite schists (“meta-greywacke” s.l.) that yield
Eoarchean and Hadean detrital zircons. These supracrustal rocks were intruded by 3100 Ma tonalites, which in turn were modified by later granitoids. Neodymium model ages of the oldest tonalites and various schists
are all >3500 Ma, and some are as old as 4200 Ma, strongly indicative of
the role of reworked Hadean/Eoarchean crust. The Assean Lake rocks
underwent multiple metamorphic episodes and migmatization. Little
else is known of these rocks. A solitary detrital 3940 Ma zircon was
reported from a drill core from the ca. 1700 Ma Thelon Basin in Nunavut
(Palmer et al., 2004), and detrital zircons from a fuchsitic quartzite of the
Rae Province in northern Canada to the east of the AGC likewise contain a
sprinkling of old detrital zircons with age distribution peaks at 3860, 3760
and 3720 Ma (Hartlaub et al., 2006).
6.6. Source(s) of the oldest detrital zircons of the Narryer Gneiss Complex
do not appear to be represented outside of Western Australia
It is worth noting that the dominant population of pre-3800 Ma ages
for detrital zircons from ca. 3300 Ma Narryer Gneisses as tabulated in
Holden et al. (2009) resembles the published ages of the oldest (igneous) components of the Acasta Gneiss Complex (ca. 4020–4050 Ma;
e.g. Stern and Bleeker, 1998). Nevertheless, compelling evidence is lacking for a link between the Narryer Gneiss complex and any other rock
Quartzites
Paragneiss
Conglomerate
BIF
Trondhjemite
Mafic Dike
Average weathering
trend predicted for
upper continental
granite
average granite composition
(Nesbitt and Young 1989)
CaO + Na2O
K2O
Fig. 7. Na2O + CaO − Al2O3 − K2O diagram showing weathering trends for the samples
in this work. Quartzites (BT0606, -08, 11) are shown as gray asterisks, the paragneiss
(BT0610) is shown as an open triangle, the conglomerate an open circle, the BIF an
open square, the trondhjemite (BT1004) a filled gray square, and the mafic dike
(BT0602) a filled black diamond. The arrow shows the average weathering trend predicted for upper continental granite from Nesbitt and Young (1989).
55
outside of the terranes captured within the Yilgarn Craton. Significantly,
the long tail in the distribution of older ages reported in Holden et al.
(2009) from the Jack Hills to 4380 Ma is so far unmatched by any
other detrital zircon locality yet discovered (Nutman et al., 2001).
Such a substantial difference in the age distributions between the
Australian and North American Paleoarchean detrital zircon record
may be used to build the case that a distinct very old continental core
with diverse primordial crustal components (accreted terrane? recycled
supracrustal belt?) existed in the vicinity of what is now the Yilgarn
block in Western Australia about 3300 million years ago.
Turning attention now to sources of Hadean zircons in North
America, other clues about the origin(s) of the Quad Creek zircons
may be found in the composition and population statistics of zircons
from the (younger) ca. 2800 Ma Central Slave Cover Group (CSCG) in
Canada (Sircombe et al., 2001). Quartzites of CSCG unconformably overlay 3000–4000 Ma tonalitic to dioritic gneisses and foliated granites of
the Central Slave Basement Complex (Bleeker et al., 1999; Pietranik et
al., 2008). The oldest zircon noted from the CSCG comes from fuchsitic
quartzite at Dwyer Lake and was dated at 3918± 5 Ma (spot 65.1,
101% concordant, [Th/U]zrc = 0.6 as reported in Sircombe et al., 2001).
The remainder of the Dwyer Lake zircons range from highly discordant
(66%) minimum ages of 2439 Ma to within 6% of concordia at 3885 Ma
([Th/U]zrc = 0.560) and 3901 Ma ([Th/U]zrc = 0.486). Like the Quad
Creek zircons investigated here, the oldest CSCG ages from Dwyer
Lake are evocative of contamination from an ancient source (Bleeker,
2003; Reddy and Evans, 2009), perhaps by a previously more extensive
“Slave Continent”?
7. Conclusions
Fine-scale geology and geochemistry of the eastern Beartooth
Mountains provide a valuable snapshot in miniature of the long and
complex history of the Wyoming Craton. Detrital/xenocrystic zircons
with Eoarchean to Hadean ages confirm that older crustal components
of the Wyoming Craton existed in the vicinity of the sedimentary
sources of these quartzites and happen to be comparable to the oldest
ages reported for the Acasta Gneiss Complex. Our work bolsters the
case for a genetic link between at least some parts of the Wyoming
Craton (e.g. the Beartooth quartzites) and the geology of the Western
Slave Province as previously suggested by Mueller et al. (1992). We further propose that the Assean Lake Complex (Böhm et al., 2000) was also
extensively contaminated by a background of “Slave Continent” detritus. Our comparison of the [Th/U]zrc ratios and 207Pb/206Pb ages of the
most concordant grains (b5% discordant) of this study with those of zircons from the Beartooth Mountains, Assean Lake Complex and the
Central Slave Cover Group shows highly variable [Th/U]zrc values at
3200 Ma, but similar age spectra and compositions for the oldest and
most concordant grains (Fig. 6). Hadean zircons shed from a previously
larger and more exposed “Slave Continent” that was variably exposed
and eroded at different times in geologic history could explain this
result.
Based on our current state of knowledge, the oldest terrestrial zircons that are found in the Narryer Gneisses and neighboring terranes
came from a unique Yilgarn source that seems not to have affected
any other Paleoarchean sedimentary catchments thus far sampled
outside of Western Australia.
Our new data contribute to resolving the relation of ages with the
regional geology of this part of the Wyoming Craton, and provide additional information towards correlating ancient terranes (Reddy and
Evans, 2009). Paleoarchean sedimentary enclaves occupy much of the
supracrustal inventory of southwestern Montana (e.g. Tobacco Root
Mountains and MMP). The oldest sediment source(s) of the Beartooth
quartzites may have a common origin with that which contaminated
the supracrustals of the Assean Lake Complex (Manitoba), and much
later, the Thelon Basin (Nunavut) and other quartzites on the Slave
Craton with pre-3900 Ma zircons. If our hypothesis is correct, this
56
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
would mean that some other Paleoarchean supracrustals of northern
North America were at one time flanking a larger Slave landmass. If
the ca. 3960 Ma Acasta Gneisses are the core remnants of this landmass
now buried or destroyed (Ernst and Bleeker, 2010), it would be the logical source of this detritus. Our model predicts that other Paleoarchean
catchments such as in the Minnesota River Valley (Bickford et al., 2006)
should also contain some low level Hadean/Eoarchean detritus. Future
studies ought to therefore consider an expanded campaign of directed
sample searches for pre-3900 Ma zircons in such enclaves in the
broader effort to quantify the extent that Hadean crust lingered on in
the Archean.
Supplementary data including complete data for geochemistry
and extended geochronology (ages only), depth profile, and cathodoluminescence image of Bear-2_5-6, back-scattered electron images of
several zircons for each age population of this study, as well as field
photographs can be found in the online version at http://dx.doi.org/
10.1016/j.chemgeo.2012.04.005.
Acknowledgments
We owe special thanks to Gina Cianciola, Amanda Engle, and
Elizabeth Frank for field assistance. Furthermore, we are grateful
to the National Geographic Society, the Colorado Scientific Society
and NASA Exobiology Program (grant “Investigating the Hadean
Earth”) for support of this work. Additional funding came from the
J.W Fulbright Foundation and the Alfred P. Sloan Foundation. Sample BT1 was collected by Julia Barczyk (University of Chicago) and
generously donated to us by Munir Humayun. Editorial advice by
Laurie Reisberg helped greatly to enhance the manuscript. Discussions with Paul Mueller and thorough comments by Wouter Bleeker
and an anonymous reviewer, are appreciated. The UCLA National Ion
Microprobe Facility is supported in part by the NSF Instrumentation
and Facilities Program.
References
Abramov, O., Mojzsis, S.J., 2009. Microbial habitability of the terrestrial biosphere during the late heavy bombardment. Nature 459, 419–422.
Amelin, Y., Kamo, S.L., Lee, D.-.C., 2011. Evolution of early crust in chondritic or nonchondritic Earth inferred from U–Pb and Lu–Hf data for chemically abraded zircon
from the Itsaq Gneiss Complex, West Greenland. Canadian Journal of Earth Sciences 48, 141–160.
Barker, F., 1979. Trondhjemite: definition, environment and hypothesis of origin. In:
Barker, F. (Ed.), Trondhjemites, Dacites and Related Rocks. Elsevier, Amsterdam,
pp. 1–12.
Bickford, M.E., Wooden, J.L., Bauer, R.L., 2006. SHRIMP study of zircons from early
Archean rocks in the Minnesota River Valley: implications for the tectonic history
of the Superior Province. GSA Bulletin 118, 94–108.
Black, L.P., Kamo, S.L., Williams, I.S., Mundil, R., Davis, D.W., Korsch, R.J., Foundoulis, C.,
2003. The application of SHRIMP to Phanerozoic geochronology; a critical appraisal
of four zircon standards. Chemical Geology 200, 171–188.
Bleeker, W., 2003. The late Archean record: a puzzle in ca. 35 pieces. Lithos 71, 99–134.
Bleeker, W., 2004. Towards a ‘natural’ time scale for the Precambrian — a proposal.
Lethaia 37, 219–222.
Bleeker, W., Ketchum, J.W.F., Davis, W.J., 1999. The Central Slave Basement Complex,
Part II: age and tectonic significance of high-strain zones along the basementcover contact. Canadian Journal of Earth Sciences 36, 1111–1130.
Blichert-Toft, J., Albarède, F., 2008. Hafnium isotopes in Jack Hills zircons and the formation of the Hadean crust. Earth and Planetary Science Letters 265, 686–702.
Blundy, J., Wood, B., 2003. Mineral-melt partitioning of uranium, thorium, and their
daughters. Reviews in Mineralogy and Geochemistry 52, 59–123.
Böhm, C.O., Heaman, L.M., Creaser, R.A., Corkery, M.T., 2000. Discovery of pre-3.5 Ga exotic crust at the northewestern Superior Province margin, Manitoba. Geology 28,
75–78.
Böhm, C.O., Heaman, L.M., Stern, R.A., 2003. Nature of Assean lake ancient crust, Manitoba: a combined SHRIMP-ID-TIMS U–Pb geochronology and Sm–Nd isotope
study. Precambrian Research 126, 55–94.
Böhm, C.O., Hartlaub, R.P., Heaman, L.M., 2007. The Assean Lake Complex: ancient crust at
the northwestern margin of the Superior Craton, Manitoba Canada. In: Van Kranendonk,
M.J., Smithies, R.H., Bennett, V.C. (Eds.), Earth's oldest Rocks. In: Condie, K.C. (Ed.), Developments in Precambrian Geology, vol. 15. Elsevier, pp. 751–773.
Bolhar, R., Kamber, B.S., Moorbath, S., Whitehouse, M.J., Collerson, K.D., 2004. Characterization of early Archean chemical sediments by trace element signatures.
Earth and Planetary Science Letters 222, 43–60.
Bowring, S.A., Housh, T., 1995. The Earth's early evolution. Science 269, 1535–1540.
Bowring, S.A., Williams, I.S., 1999. Priscoan (4.00–4.03 Ga) orthogneisses from northwestern Canada. Contributions to Mineralogy and Petrology 134, 3–16.
Bowring, S.A., Williams, I.S., Compston, W., 1989. 3.96 Ga gneisses from the Slave Province, Northwest-Territories, Canada. Geology 17, 971–975.
Cates, N.L., Mojzsis, S.J., 2006. Chemical and isotopic evidence for widespread Eoarchean metasedimentary enclaves in southern West Greenland. Geochimica et Cosmochimica Acta 70, 4229–4257.
Cates, N.L., Mojzsis, S.J., 2007. Pre-3750 Ma supracrustal rocks from the Nuvvuagittuq
supracrustal belt, northern Quebec. Earth and Planetary Science Letters 255,
9–21.
Cates, N.L., Mojzsis, S.J., 2009. Metamorphic zircon, trace elements and Neoarchean
metamorphism in the ca. 3.75 Ga Nuvvuagittuq supracrustal belt, Quebec
(Canada). Chemical Geology 261, 98–113.
Chamberlain, K.R., Mueller, P.A., 2007. Oldest rocks of the Wyoming Craton, In: Van
Kranendonk, M.J., Smithies, R.H., Bennett, V. (Eds.), Earth's Oldest Rocks, Developments in Precambrian Geology series, Kent Condie, series ed. Elsevier, pp. 775–791.
Chamberlain, K.R., Frost, C.D., Frost, B.R., 2003. Early Archean to Mesoproterozoic evolution of the Wyoming Province: Archean origins to modern lithospheric architecture. Canadian Journal of Earth Sciences 40, 1357–1374.
Compston, W., Pidgeon, R.T., 1986. Jack Hills, Evidence of more very old detrital zircons
in Western-Australia. Nature 321, 766–769.
Corfu, F., Hanchar, J.M., Hoskin, P.W.O., Kinny, P., 2003. Atlas of zircon textures. Reviews in Mineralogy and Geochemistry 53, 469–500.
Eckelmann, F.D., Poldervaart, A., 1957. Geologic evolution of the Beartooth Mountains,
Montana and Wyoming. GSA Bulletin 68, 1225–1262.
Ernst, R., Bleeker, W., 2010. Large igneous provinces (LIPs), giant dike swarms, and
mantle plumes: significance for breakup events within Canada and adjacent regions from 2.5 Ga to the Present. Canadian Journal of Earth Sciences 47, 695–739.
Fisher, L.B., Stacey, J.S., 1986. Uranium-lead zircon ages and common lead measurements for the Archean gneisses of the Granite Mountains, Wyoming. U.S. Geological Survey Bulletin 1622, 13–23.
Froude, D.O., Ireland, T.R., Kinny, P.D., Williams, I.S., Compston, W., Williams, I.R., 1983.
Ion microprobe identification of 4,100–4,200 Myr-old terrestrial zircons. Nature
304, 616–618.
Galer, S.J.G., Goldstein, S.L., 1991. Early mantle differentiation and its thermal consequences. Geochimica et Cosmochimica Acta 55, 227–239.
Grace, R.L.B., Chamberlain, K.R., Frost, B.R., Frost, C.D., 2006. Tectonic histories of the
Paleoarchean to Mesoarchean Sacawee Block and Neoarchean Oregon Trail structural belt of the south-central Wyoming Province. Canadian Journal of Earth Sciences 43, 1445–1466.
Harley, S.L., Black, L.P., 1997. A revised Archean chronology for the Napier Complex,
Enderby Land, from SHRIMP ion-microprobe studies. Antarctic Science 9, 74–91.
Harrison, T.M., 2009. The Hadean Crust: evidence from >4 Ga Zircons. Annual Review
of Earth and Planetary Sciences 37, 479–505.
Hartlaub, R.P., Heaman, L.M., Simonetti, A., Böhm, C.O., 2006. Relicts of Earth's earliest
crust: U–Pb, Lu–Hf, and morphological characteristics of >3.7 Ga detrital zircon
of the western Canadian Shield. Geological Society of America Special Paper 405,
75–89.
Hay, D.C., Dempster, T.J., Lee, M.R., 2010. Anatomy of low temperature zircon outgrowth. Contributions to Mineralogy and Petrology 159, 81–92.
Henry, D.J., Mueller, P.A., Wooden, J.L., Warner, J.L., Lee-Berman, R., 1984. Granulite
grade supracrustal assemblages of the Quad Creek area, eastern Beartooth Mountains, Montana. In: Mueller, P.A., Wooden, J.L. (Eds.), Precambrian Geology of the
Beartooth Mountains, Montana and Wyoming: Montana Bureau of Mines and Geology Special Publication, pp. 147–159.
Holden, P., Lanc, P., Ireland, T.R., Harrison, T.M., Foster, J.J., Bruce, Z., 2009. Mass-spectrometric mining of Hadean zircons by automated SHRIMP multi-collector and
single-collector U/Pb zircon age dating: the first 100,000 grains. International Journal of Mass Spectrometry and Ion Processes 286, 53–63.
Hopkins, M., Harrison, T.M., Manning, C.E., 2008. Low heat flow inferred from > 4 Gyr
zircons suggests Hadean plate boundary interactions. Nature 456, 493–496.
Hopkins, M.D., Harrison, T.M., Manning, C.E., 2010. Constraints on Hadean geodynamics from mineral inclusions in > 4 Ga zircons. Earth and Planetary Science Letters 298, 367–376.
Hoskin, P.W.O., Schaltegger, U., 2003. The composition of zircon and igneous metamorphic petrogenesis. Reviews in Mineralogy and Geochemistry 53, 27–62.
Iizuka, T., Horie, Kl, Komiya, T., Maruyama, S., Hirata, T., Hidaka, H., Windley, B.F., 2006.
4.2 Ga zircon xenocryst in an Acasta geniss from northwestern Canada: evidence
for early continental crust. Geology 34, 245–248.
Iizuka, T., Komiya, T., Ueno, Y., Katayama, I., Uehara, Y., Maruyama, S., Hirata, T.,
Johnson, S.P., Dunkley, D.J., 2007. Geology and geochronology of the Acasta Gneiss
Complex, northwestern Canada: new constraints on its tectonothermal history.
Precambrian Research 153, 179–208.
Irvine, T.N., Baragar, W.R.A., 1971. A guide to the chemical classification of the common
volcanic rocks. Canadian Journal of Earth Sciences 8, 523–548.
Kamber, B.S., 2007. The enigma of the terrestrial protocrust: evidence for its former existence and the importance of its complete disappearance. In: Van Kranendonk,
M.J., Smithies, H., Bennett, V. (Eds.), Earth's Oldest Rocks. : Developments in Precambrian Geology, 15. Elsevier, Amsterdam, pp. 75–89.
Kemp, A.I.S., Wilde, S.A., Hawkesworth, C.J., Coath, C.D., Nemchin, A., Pidgeon, R.T.,
Vervoort, J.D., DuFrane, S.A., 2010. Hadean crustal evolution revisited: new constraints from Pb–Hf isotope systematics of the Jack Hills zircons. Earth and Planetary Science Letters 296, 45–56.
King, J.E. 1985. Structure of the metamorphic internal zone, Northern Wopmay Orogen,
Northwest Territories, Canada. Queen's University, Ontario, unpublished Ph.D. thesis, 208 pp.
A.C. Maier et al. / Chemical Geology 312-313 (2012) 47–57
Konhauser, K.O., Pecoits, E., Lalonde, S.V., Papineau, D., Nibset, E.G., Barley, M.E., Arndt,
N.T., Zahnle, K., Kamber, B.S., 2009. Oceanic nickel depletion and a methanogen
famine before the Great Oxidation Event. Nature 458, 750–753.
Konhauser, K.O., Lalonde, S.V., Planavsky, N., Pecoits, E., Lyons, T.W., Mojzsis, S.J.,
Rouxel, O.J., Barley, M.E., Rosiere, C., Fralick, P.A., Kump, L.R., Bekker, A., 2011. Chromium abundances in iron formations record Earth's earliest acid rock drainage
during the Great Oxidation Event. Nature 478, 369–373.
Kuno, H., 1968. Differentiation of basalt magmas. In: Hess, H.H., Poldervaart, A. (Eds.),
Basalts: The Poldervaart Treatise on Rocks of Basaltic Composition, vol. 2. Interscience, New York, pp. 623–688.
Langstaff, G.D., 1995. Archean geology of the Granite Mountains, Wyoming. Unpublished Ph.D. dissertation, Colorado School of Mines, Golden, Colorado.
Ludwig, K.R., 2003. User's Manual for Isoplot/Ex: A Geochronological Toolkit for Microsoft Excel, Berkley Geochronological Center Special Publication.
Maas, R., McCulloch, M.T., 1991. The provenance of Archean clastic metasediments in
the Narryer Gneiss Complex, western Australia — trace-element geochemistry,
Nd isotopes, and U–Pb ages for detrital zircons. Geochimica et Cosmochimica
Acta 55, 1915–1932.
Mahood, G., Hildreth, W., 1983. Large partition coeffecients for trace elements in highsilica rhyolites. Geochimica et Cosmochimica Acta 47, 11–30.
Manning, C.E., Mojzsis, S.J., Harrison, T.M., 2006. Geology, age and origin o fsupracrustal
rocks at Akilia, West Greenland. American Journal of Science 306, 303–366.
Mogk, D., Henry, D., 1988. Metamorphic petrology of the northern Archean Wyoming
Province, SW Montana: evidence for Archean collisional tectonics. In: Ernst, W.
(Ed.), Metamorphism and Crustal Evolution in the Western US. Prentice Hall,
Englewood Cliffs, NJ, pp. 363–382.
Mogk, D.W., Mueller, P.A., Wooden, J.L., 1988. Archean tectonics of the North Snowy
Block, Beartooth Mountains, Montana. Journal of Geology 96, 125–141.
Mogk, D.W., Mueller, P.A., Wooden, J.L., 1992. The nature of Archean terrane boundaries —
an example from the northern Wyoming Province. Precambrian Research 55, 155–168.
Mojzsis, S.J., Harrison, T.M., 2002. Establishment of a 3.83-Ga magmatic age for the
Akilia tonalite (southern West Greenland). Earth and Planetary Science Letters
202, 563–576.
Mojzsis, S.J., Harrison, T.M., Pidgeon, R.T., 2001. Oxygen isotope evidence from ancient
zircons for liquid water at Earth's surface 4,300 Myr ago. Nature 409, 178–181.
Moorbath, S., 2005. Oldest rocks, earliest life, heaviest impacts, and the HadeanArchean transition. Applied Geochemistry 20, 819–824.
Mueller, P.A., Frost, C.D., 2006. The Wyoming Province: a distinctive Archean craton in
Laurentian North America. Canadian Journal of Earth Sciences 43, 1391–1397.
Mueller, P.A., Wooden, J.L., 2012. Trace element and Lu–Hf systematics in Hadean–
Archean detritral zircons: implications for crustal evolution. Journal of Geology
120, 15–29.
Mueller, P.A., Shuster, R.D., Graves, M.A., Wooden, J.L., 1988. Age and composition of a
late Archean magmatic complex, Beartooth Mountains, Montana–Wyoming.
Montana Bureau of Mines and Geology Special Publication 96, 6–22.
Mueller, P.A., Wooden, J.L., Nutman, A.P., 1992. 3.96 Ga Zircons from an Archean
quartzite, Beartooth Mountains, Montana. Geology 20, 327–330.
Mueller, P.A., Wooden, J.L., Mogk, D.W., Nutman, A.P., Williams, I.S., 1996. Extended
history of a 3.5 Ga trondhjemitic gneiss, Wyoming Province, USA: evidence from
U–Pb systematics in zircon. Precambrian Research 78, 41–52.
Mueller, P.A., Wooden, J.L., Nutman, A.P., Mogk, D.W., 1998. Early Archean crust in the
northern Wyoming Province: evidence from U–Pb ages of detrital zircons. Precambrian Research 91, 295–307.
Nelson, D.R., Robinson, B.W., Myers, J.S., 2000. Complex geological histories extending
for ≥4.0 Ga deciphered from xenocryst zircon microstructures. Earth and Planetary Science Letters 181, 89–102.
Nesbitt, H.W., Young, G.M., 1989. Formation and diagenesis of weathering profiles.
Journal of Geology 97, 129–147.
Nutman, A.P., McGregor, V.R., Friend, C.R.L., Bennett, V.C., Kinny, P.D., 1996. The Itsaq
Geniss Complex of southern West Greenland; the world's most extensive record
of early crustal evolution (2900–2600 Ma). Precambrian Research 78, 1–39.
Nutman, A.P., Mojzsis, S.J., Friend, C.R.L., 1997. Recognition of ≥3850 Ma water-lain
sediments in West Greenland and their significance for the early Archean Earth.
Geochimica et Cosmochimica Acta 61, 2475–2484.
Nutman, A.P., Friend, C.R.L., Bennett, V.C., 2001. Review of the oldest (4400–3600 Ma)
geological and mineralogical record: glimpses of the beginning. Episodes 24,
93–101.
Nutman, A.P., Friend, C.R.L., Barker, S.L.L., McGregor, V.R., 2004. Inventory and assessment of Paleoarchean gneiss terrains and detrital zircons in southern West Greenland.
Precambrian Research 135, 281–314.
Paces, J.B., Miller, J.D., 1993. Precise U–Pb ages of Duluth Complex and related mafic intrusions, northeastern Minnesota — geochronological insights to physical petrogenetic,
57
paleomagnetic, and tectonomagmatic processes associated with the 1.1 Ga midcontinent rift system. Journal of Geophysical Research, Solid Earth 98, 13997–14013.
Palmer, S.E., Kyser, T.K., Hiatt, E.E., 2004. Provenance of the Proterozoic Thelon Basin,
Nunavut, Canada, from detrital zircon geochronology and detrital quartz oxygen
isotopes. Precambrian Research 129, 115–140.
Pietranik, A., Hawkesworth, C.J., Storey, C., Kemp, A., Sircombe, K., Whitehouse, M.,
Bleeker, W., 2008. Episodic, mafic crust formation from 4.5–2.8 Ga: new evidence
from detrital zircons, Slave craton Canada. Geology 36, 875–878.
Poldervaart, A., Bentley, R.D., 1958. Precambrian and later evolution of the Beartooth
Mountains, Montana and Wyoming. In: Zieglar, D.L. (Ed.), Ninth Annual Field Conference. Billings Geological Society, pp. 7–15.
Reddy, S.M., Evans, D.A.D., 2009. Paleoproterozoic supercontinents and global evolution: Correlations from core to atmosphere. In: Reddy, S.M., Mazumder, R., Evans,
D.A.D., Collins, A.S. (Eds.), Paleoproterozoic Supercontinents and Global Evolution:
Geol. Soc. London Spec. Pub., 232, pp. 1–26.
Rickwood, P.C., 1989. Boundary lines within petrologic diagrams which use oxides of
major and minor elements. Lithos 22, 247–263.
Rubatto, D., 2002. Zircon trace element geochemistry: partitioning with garnet and the
link between U–Pb age and metamorphism. Chemical Geology 184, 373–499.
Sano, Y., Terada, K., Hidaka, H., Yokoyama, K., Nutman, A.P., 1999. Paleoproterozoic
thermal events recorded in the 4.0 Acasta gneiss, Canada: evidence from SHRIMP
U–Pb dating of apatite and zircon. Geochimica et Cosmochimica Acta 63, 899–905.
Schafer, P.A., 1937. Chromite deposits of Montana. Montana Bureau of Mines and Geology Memoir 18, 35.
Schuhmacher, M., de Chambost, E., McKeegan, K.D., Harrison, T.M., Migeon, H., 1994.
Dating of zircon with the CAMECA IMS 1270. In: Benninghoven, A., Nihei, Y.,
Shimizu, R., Werner, H.W. (Eds.), Secondaray Ion Mass Spectrometry SIMS IX.
John Wiley & Sons, New York, pp. 912–922.
Shirey, S., Kamber, B., Whitehouse, M., Mueller, P., Basu, A., 2008. A review of the geochemical evidence for mantle and crustal processes in the Hadean and Archean:
implications for the onset of plate tectonic subduction. Geological Society of
America. Memoirs 440, 1–29.
Sircombe, K.N., Bleeker, W., Stern, R., 2001. Detrital zircon geochronology and grainsize analysis of a 2800 Ma Mesoarchean proto-cratonic cover succession, Slave
Province, Canada. Earth and Planetary Science Letters 189, 207–220.
Stern, R.A., Bleeker, W., 1998. Age of the world's oldest rocks refined using Canada's
SHRIMP, the Acasta gneiss complex, Northwest Territories, Canada. Geoscience
Canada 25, 27–31.
Stevenson, R.K., Patchett, P.J., 1990. Implications for the evolution of continental-crust
from Hf-isotope systematics of Archean detrital zircons. Geochimica et Cosmochimica
Acta 54, 1683–1697.
Taylor, S.R., Mclennan, S.M., 1985. The Continental Crust: Its Composition and Evolution. Blackwell Scientific, Oxford.
Trail, D., 2006. A Geochemical Investigation of Hadean Zircon. Unpublished Master of
Science thesis, University of Colorado, Boulder, Colorado.
Trail, D., Mojzsis, S.J., Harrison, T.M., Schmitt, A.K., Watson, E.B., Young, E.D., 2007.
Constraints on Hadean protoliths from oxygen isotopes, Ti-thermometry and rare
earth elements. Geochemistry, Geophysics, Geosystems 8, http://dx.doi.org/10.1029/
2006GC001449.
Trail, D., Watson, E.B., Tailby, N.D., 2011. The oxidation state of Hadean magmas and
implications for early Earth's atmosphere. Nature 480, 79–83.
Valley, J.W., Lackey, J.S., Cavosie, A.J., Clechenko, C.C., Spicuzza, M.J., Basei, M.A.S.,
Bindeman, I.N., Ferreira, V.P., Sial, A.N., King, E.M., Peck, W.H., Sinha, A.K., Wei,
C.S., 2005. 4.4 billion years of crustal maturation: oxygen isotopes in magmatic zircon. Contributions to Mineralogy and Petrology 150, 561–580.
Wooden, J.L., Mueller, P.A., 1988. Pb, Sr, and Nd isotopic compositions of a suite of Late
Archean igneous rocks, eastern Beartooth Mountains: implications for crust–mantle evolution. Earth and Planetary Science Letters 87, 59–72.
Wooden, J.L., Mueller, P.A., Mogk, D.W., 1988a. A review of the geochemistry and geochronology of the Archean rocks of the northern part of the Wyoming Province. In:
Ernst, W.G. (Ed.), Metamorphism and Crustal Evolution of the Western United
States. Prentice-Hall, New York, pp. 383–410.
Wooden, J.L., Mueller, P.A., Mogk, D.W., 1988b. A review of the Archean rocks of the
Beartooth Mountains, Montana and Wyoming. Montana Bureau of Mines and Geology Special Publication 96, 23–42.
Wyche, S., Nelson, D.R., Riganti, A., 2004. 4350–3130 Ma detrital zircons in the Southern Cross Granite-Greenstone Terrane, Western Australia: implications for the
early evolution of the Yilgarn Craton. Australian Journal of Earth Sciences 51,
31–45.